A markup language document such as a webpage—typically includes content that is displayed to a viewer of the document. Such content generally takes a familiar form, such as in hypertext markup language (HTML) and defines the various elements that will appear when a webpage is rendered on a computing device. The elements can include text, hyperlinks, images, animations, forms, and other such elements.
Under certain conditions, it may be desirable to display two or more different versions of a webpage to two or more different viewers. For example, one version can include content (e.g., text) that is not included in a second version.